In recent years, various types of on-chip optical interconnection for performing data input/output at high speed and low power have been proposed for achieving low-loss, high-density optical transmission. In order to realize such optical interconnection, a micro-ring LD using a micro-ring resonator is attracting attention as a small light source. Since, however, the output of this type micro-ring LD is unstable because of return light reflected from a waveguide for optical output, it is necessary to suppress the ratio of the return light to 0.01% or less.
In a light-receiving element for receiving light from the micro-ring LD, it is desired to enable the light-receiving element and the micro-ring LD to be mounted on one chip (wafer). However, it is difficult to realize a semiconductor light-receiving element that can be mounted on a single chip along with the micro-ring LD and can exhibit high efficiency and sufficiently reduced reflection.